Conventionally, acrylonitrile-styrene type copolymers (hereinafter referred to as AS type resins) are well known and has been commonly used in such applications as molding materials and the like. Specific examples thereof are acrylonitrile-styrene copolymers (hereinafter referred to as AS resins), acrylonitrile-butadiene-styrene resins (hereinafter referred to as ABS resins), and the like.
Where AS resins are used as molding materials, they are subjected to finish coating in order to impart an attractive appearance to the molded articles and maintain their properties such as weather resistance and the like. This finish coating is generally performed by using an acrylic paint. However, AS resin moldings coated with an acrylic paint involve several problems, for example, in that a peeling-off of the acrylic paint from the AS resin may frequently occur during use and thereby impair their commercial value.
As for para-isopropenylphenol, copolymers of it and acrylonitrile or styrene have been investigated respectively. However, the performance characteristics of these copolymers are not thoroughly known. According to the findings of the present inventors, it has been determined that, when added to AS resins, the former copolymer exhibits poor miscibility therewith and can hardly produce any desired improvement in adhesion properties. The latter copolymer involves no problem concerning miscibility with AS resins, but have no appreciable effect in improving adhesion properties.
In order to overcome the above-described disadvantages of AS resins, the present inventors have made intensive and extensive studies and have found that certain copolymers obtained by copolymerization of acrylonitrile, styrene, and para-isopropenylphenol have excellent heat resistance and adhesion properties and, when used as modifying agents for AS resins, can improve the adhesion between the AS resin moldings and the acrylic paint.